The aim of the proposal is to develop a method for high precision quantitative assessment of the hemodynamic significance of obstructive lesions in coronary arteries from coronary arteriograms. Coronary arteriography is a widely practiced clinical diagnostic method which is able to identify graphically the extent and location of obstructive lesions in the coronary arteries of man. Quantitation of these lesions and assessment of their functional implications is presently performed by visual reading of the projected films. This method is subjective and, therefore, believed to be imprecise and inadequate. Methods based on roentgen densitometry are suitable to record objectively the angiographic events. Among these, a technique which uses a high precision mechanical scanner with 50 times 50 scanning aperture and the ability to distinguish 128 reproducible gray levels within the optical density range of 0-2 optical density units will be applied. The scan data will be analyzed by digital scanner indirect interaction with the interpreter of the angiogram. High precision densitometric evaluation of angiographically identified stenotic lesions will be performed. The analysis will also aim at the relative turnover rate of the contrast agent within different areas of the non-obstructed or obstructed coronary artery tree. It is expected that the latter data can be fitted into mathematical functions. Successful conduction of the study should result in a new technique for retrieval of functional information from the coronary arteriogram. Such a method will provide considerable improvement of our understanding of physiology and pathophysiology of the coronary circulation and be helpful to assess proper indications for the management of patients with coronary heart disease.